1. Field of the Invention
The present invention relates to pigments and chemical groups attached onto pigments. More particularly, the present invention relates to improved methods for attaching a variety of different types of chemical groups, such as polymers, onto pigments.
2. Description of Related Art
Methods exist for the grafting of polymers to the surface of carbon black which contain specific surface groups (e.g., phenols and carboxyl groups), such as with channel blacks. However, these methods are not easily applied to the surface grafting of polymers onto furnace and acetylene blacks, because these carbon blacks generally lack these specific functional groups. The methods described herein have the advantage that allows for the surface grafting of polymers to the surface of carbon black, regardless of the inherent functional groups.
Pigments having polymers grafted to their surface have been found to provide improved performance when used in an inkjet ink. These materials afford printed images which are notably more waterfast, highlighter smearfast, and smudge resistant than conventional inks. The printed images also show improved edge acuity and intercolorbleed properties. The dispersion stability is also greatly improved.
U.S. Pat. No. 5,851,280 discloses methods for the attachment of organic groups onto pigments, including via a diazonium reaction wherein the organic group is part of the diazonium salt. Through reaction with a pigment, like carbon black, the organic group attaches onto the pigment. These modified pigments can be used in a variety of applications, such as inks, inkjet inks, coatings, toners, plastics, rubbers, and the like.
There is a desire by those in the industry to further develop methods of attaching organic groups, and primarily polymers, onto pigments for the same and similar applications described above. These additional methods may provide advantageous alternatives to forming modified pigments.
A feature of the present invention is to provide improved methods for the attachment of chemical groups, including polymers, onto pigments.
A further feature of the present invention is to provide novel modified pigments and compositions containing them, such as inks and coatings.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention relates to a method of making a modified pigment by attaching at least one chemical group onto a pigment. The method involves reacting a pigment having attached a first chemical group with a second chemical group to form a pigment having attached a third chemical group, wherein the second chemical group reacts with the first chemical group to form the third chemical group. The first chemical group contains at least one nucleophile and the second chemical group contains at least one electrophile, or vice versa. Preferably, in this method, the second chemical group is a polymer or contains a polymer.
The present invention further relates to a modified pigment comprising a pigment having attached at least one organic group, wherein the organic group comprises the reaction product of at least one (2-sulfatoethyl)-sulphone group and at least one nucleophilic polymer.
The present invention further relates to a modified pigment comprising a pigment having attached at least one organic group, wherein the organic group comprises the reaction product of at least one benzoic acid group and at least one nucleophilic polymer.
The present invention further relates to a modified pigment comprising a pigment having attached at least one organic group, wherein the organic group comprises the reaction product of at least one electrophile and at least one nucleophilic polymer; and an acylating agent.
The present invention further relates to ink compositions containing the modified pigments described above. The modified pigments of the present invention also have a variety of uses in coatings, plastics, rubbers, toners, and the like.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.